Multi-stage seal for well fracturing

ABSTRACT

A fracturing system including a ring gasket disposed between a fracturing tree and a wellhead component is provided. In one embodiment, the ring gasket includes multiple sealing stages that seal against grooves in the fracturing tree and the wellhead component. The ring gasket may also include one or more recesses between the sealing stages. In some embodiments, the ring gasket has a configuration that reduces gasket setting load and increases flange separation load compared to other gaskets used in fracturing operations. And in some embodiments, the system enables monitoring of gasket sealing integrity, even during fracturing operations. Additional systems, devices, and methods are also disclosed.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the presently describedembodiments. This discussion is believed to be helpful in providing thereader with background information to facilitate a better understandingof the various aspects of the present embodiments. Accordingly, itshould be understood that these statements are to be read in this light,and not as admissions of prior art.

In order to meet consumer and industrial demand for natural resources,companies often invest significant amounts of time and money in findingand extracting oil, natural gas, and other subterranean resources fromthe earth. Particularly, once a desired subterranean resource such asoil or natural gas is discovered, drilling and production systems areoften used to access and extract the resource. These systems may belocated onshore or offshore depending on the location of a desiredresource. Further, such systems generally include a wellhead assemblythrough which the resource is extracted. These wellhead assemblies mayinclude a wide variety of components, such as various casings, valves,fluid conduits, and the like, that aid drilling or extractionoperations.

Additionally, such wellhead assemblies may use a fracturing tree andother components to fracture a well and enhance production. As will beappreciated, resources such as oil and natural gas are generallyextracted from fissures or other cavities formed in various subterraneanrock formations or strata. To facilitate extraction of such resources, awell may be subjected to a fracturing process that creates one or moreman-made fractures in a rock formation. This helps couple pre-existingfissures and cavities, allowing oil, gas, or the like to flow into thewellbore. Such fracturing processes typically include injecting afracturing fluid—often a mixture including sand and water—into the wellto increase the well's pressure and form the man-made fractures.

SUMMARY

Certain aspects of some embodiments disclosed herein are set forthbelow. It should be understood that these aspects are presented merelyto provide the reader with a brief summary of certain forms theinvention might take and that these aspects are not intended to limitthe scope of the invention. Indeed, the invention may encompass avariety of aspects that may not be set forth below.

Embodiments of the present disclosure generally relate to wellfracturing operations. In some embodiments, a fracturing tree and awellhead component (e.g., a tubing spool) are joined via a flangedconnection that includes a ring gasket with multiple sealing stages. Inone embodiment, the ring gasket includes at least one recess in the bodyof the ring gasket between the sealing stages to decrease gasket settingload and increase flange separation load of the fracturing tree and thewellhead component. Additionally, some embodiments include a test portconnected to a sealing groove in which the ring gasket is disposed,enabling the sealing integrity of the ring gasket to be monitored duringfracturing.

Various refinements of the features noted above may exist in relation tovarious aspects of the present embodiments. Further features may also beincorporated in these various aspects. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to one or more of theillustrated embodiments may be incorporated into any of theabove-described aspects of the present disclosure alone or in anycombination. Again, the brief summary presented above is intended onlyto familiarize the reader with certain aspects and contexts of someembodiments without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of certain embodimentswill become better understood when the following detailed description isread with reference to the accompanying drawings in which likecharacters represent like parts throughout the drawings, wherein:

FIG. 1 generally depicts a resource extraction system having a wellheadassembly that may be connected to a production tree or a fracturing treeto facilitate production from a well in accordance with an embodiment ofthe present disclosure;

FIG. 2 is an elevational view of a fracturing tree installed on acomponent of a wellhead assembly in accordance with one embodiment;

FIG. 3 is a cross-section of the connection between the fracturing treeand the wellhead component of FIG. 2 in accordance with one embodimentand includes an example of a ring gasket for sealing between thefracturing tree and the wellhead component;

FIG. 4 is a perspective view of the ring gasket of FIG. 3 removed frombetween the fracturing tree and the wellhead component;

FIG. 5 is a cross-section of the ring gasket depicted in FIG. 4;

FIG. 6 is a detail view of a portion of the fracturing tree connectiondepicted in FIG. 3 having a test port connected to a sealing groove inwhich the ring gasket is disposed to enable monitoring of gasket sealingintegrity during a fracturing operation in accordance with oneembodiment; and

FIG. 7 is a block diagram that represents a method for monitoring gasketintegrity and controlling fracturing operations in accordance with oneembodiment.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments, the articles “a,”“an,” “the,” and “said” are intended to mean that there are one or moreof the elements. The terms “comprising,” “including,” and “having” areintended to be inclusive and mean that there may be additional elementsother than the listed elements. Moreover, any use of “top,” “bottom,”“above,” “below,” other directional terms, and variations of these termsis made for convenience, but does not require any particular orientationof the components.

Turning now to the drawings, a resource extraction system 10 isillustrated in FIG. 1 by way of example. The depicted system 10facilitates extraction of natural resources (e.g., oil or natural gas)from a well 12 via a wellbore 14 and a wellhead assembly 16. Thewellhead assembly 16 may include a variety of components, such as awellhead, a casing head, a tubing spool, and valves that control theflow of fluids through the assembly. In the presently illustratedembodiment, the well 12 is a surface well in that the equipment of thewellhead assembly 16 is installed at ground level on dry land. But itwill be appreciated that in different embodiments the resourceextraction system 10 may be provided in other environments, such as inconnection with subsea or platform wells.

A production tree 18 is connected to the wellhead assembly 16 (e.g., toa tubing spool) and facilitates extraction of the natural resource fromthe well 12. In some instances, and to further facilitate production, afracturing tree 20 may be connected to the wellhead assembly 16. Byinjecting a fracturing fluid into the well 12 via the fracturing tree20, the system 10 increases the number or size of fractures in aresource-bearing rock formation (or strata) to enhance recovery of thedesired resource.

A particular arrangement 24 of a fracturing tree 20 connected to awellhead assembly 16 is depicted in FIG. 2 by way of further example.The arrangement 24 includes various valves 26 for controlling fluid flowthrough the wellhead assembly 16 and the fracturing tree 20. Fracturingfluid may be pumped from a source into the fracturing tree 20 through afracturing head 28 (also known as a goat head). The fracturing tree 20is connected to a component 30 of the wellhead assembly 16. In oneembodiment, the component 30 is a tubing spool of the wellhead assembly16. But it is noted that the fracturing tree 20 could instead beconnected to another component of the wellhead assembly 16.

The connection of the fracturing tree 20 to the component 30 may bereferred to as a fracturing connection. And in the present depiction,the fracturing tree 20 and the component 30 include respective flanges32 and 34 (depicted as ring joint type flanges) joined together withfasteners 36 (such as nuts with studs of a studded flange 34), thoughother fasteners or manners of connecting the tree 20 and the component30 could instead be used. Consequently, in those embodiments having suchflanges, this connection between the fracturing tree 20 and thecomponent 30 may also be referred to as a flanged connection. In atleast some embodiments, the flanges 32 and 34 conform to AdvancedPetroleum Institute (API) Specification 6A (i.e., the flanges 32 and 34are API flanges). And in at least some of these embodiments the flanges32 and 34 conform to the specifications of 6BX flanges in APISpecification 6A (i.e., the flanges 32 and 34 are 6BX flanges).

Additional details about the fracturing connection of arrangement 24 areillustrated in the cross-section of FIG. 3 in accordance with oneembodiment. As depicted, the connection of the fracturing tree 20 andthe wellhead component 30 allow fluid to pass between their respectivebores 40 and 42. The fracturing connection includes a ring gasket 44 toinhibit fluids from leaving the bores through the connection. The ringgasket 44 is positioned within and seals against opposing sealinggrooves 46 and 48 of the fracturing tree 20 and the wellhead component30. And in at least some embodiments the region of the fracturingconnection in which the ring gasket 44 is disposed is connected by aconduit 50 to a test port 52. As discussed in greater detail below, suchan arrangement enables measurement of pressure within the sealinggrooves and monitoring of gasket sealing integrity.

In one embodiment generally depicted in FIGS. 4 and 5, the ring gasket44 takes the form of a two-stage sealing gasket having an outer endportion or stage 56 and an inner end portion or stage 58. The outer end56 of the ring gasket 44 includes outer sealing surfaces 60 and 62,while the inner end 58 includes inner sealing surfaces 64 and 66. Thesealing surfaces seal against the grooves 46 and 48 of the fracturingtree 20 and the wellhead component 30 to inhibit leaking from the bores40 and 42 at the fracturing connection. The ring gasket 44 may be formedof any suitable material, such as stainless steel. And, if desired, anyor all of the ring gasket 44, the sealing groove 46, and the sealinggroove 48 may include suitable coatings or platings, such as those thatfacilitate sealing engagement or minimize galling.

As noted above, the flanges 32 and 34 of some embodiments are 6BXflanges. API Specification 6A also defines a class of BX gaskets, andstates that only such BX gaskets shall be used with 6BX flanges. Butcontrary to this instruction, in at least some embodiments (includingthat illustrated in FIG. 3) the ring gasket 44 installed between 6BXflanges 32 and 34 is not a BX gasket. For instance, the body of the ringgasket 44 may also include one or more recesses, such as the pair ofopposing recesses 68 shown in FIG. 5. In the depicted embodiment, therecesses 68 are provided as circumferential grooves between the outerand inner sealing surfaces and generally separate the outer and innerend stages 56 and 58. Such an arrangement provides for lower gasketsetting load (requiring less preload on the flanged connection toenergize the seals of the gasket) in comparison to some other ringgaskets, such as BX ring gaskets defined in API Specification 6A. Inturn, the depicted non-BX ring gasket 44 also provides increased flangeseparation load at the connection, allowing the connection to maintainsealing integrity while experiencing greater external forces (e.g., frombending moments and vibration) on the fracturing tree as compared tosome other ring gaskets.

The ring gasket 44 also includes a pressure port 70 extending axiallythrough its body. With reference to FIG. 6, this pressure port 70 allowsbalancing of pressure between a region 72 within the sealing groove 46of the fracturing tree 20 (between sealing surfaces 62 and 66 of thering gasket 44) and a region 74 within the sealing groove 48 of thewellhead component 30 (between sealing surfaces 60 and 64 of the gasket44).

As depicted in FIG. 6, the sealing surfaces 62 and 60 seal against theouter sides of the sealing grooves 46 and 48 and isolate the regions 72and 74 from external pressure about the flanges 32 and 34 of thefracturing tree 20 and the wellhead component 30. Likewise, the sealingsurfaces 66 and 64 seal against the inner sides of the sealing grooves46 and 48 and isolate the regions 72 and 74 from internal pressurewithin the bores 40 and 42 of the fracturing tree 20 and the wellheadcomponent 30. In contrast to previous arrangements in which a ringgasket was intended to continuously seal only against the inner sides ofthe sealing grooves (and only intermittently seal against the outersides of the sealing grooves), in at least one embodiment of the presentdisclosure the ring gasket 44 is configured to maintain sealing alongboth the inner and outer surfaces of the sealing grooves 46 and 48.

The test port 52 is connected to the region 74 by the conduit 50. And asnoted before, the region 74 is connected to the region 72 by thepressure port 70. The isolation of pressure within the regions 72 and 74from pressure about the fracturing tree 20 and the wellhead component 30and from pressure within the bores 40 and 42 facilitates monitoring ofthe sealing integrity of the ring gasket 44 in one embodiment. In oneinstance, the test port 52 may be used before a fracturing operation toensure proper setting and adequate sealing of the ring gasket 44. Forexample, in an embodiment in which the ring gasket 44 is intended tomaintain sealing at both the outer and inner stages 56 and 58 onceinstalled in the sealing grooves 46 and 48, the regions 72 and 74 may bepressurized via the test port 52 and conduit 50. If both stages 56 and58 are properly sealing against the grooves 46 and 48, the regions 72and 74 will maintain the applied pressure. If not, the regions 72 and 74will lose pressure, indicating loss of sealing integrity. Such testingmay, of course, be performed after a fracturing operation as well.

But in addition to testing before or after operation, certainembodiments also allow the pressure within the regions 72 and 74 to bemonitored via the test port 52 during operation of the wellheadassembly. If the initial pressure in the regions 72 and 74 is betweenthe environmental pressure outside the wellhead assembly and thepressure in the bores 40 and 42 in operation (e.g., the fracturingpressure in a fracturing operation), loss of sealing integrity of thering gasket 44 will cause a change in the pressure in the regions 72 and74. Particularly, loss of sealing integrity at inner sealing surfaces 64or 66 will cause fluid from the bores 40 and 42 to leak into the regions72 or 74, generally increasing the pressure in these regions.Alternatively, loss of sealing integrity at outer sealing surfaces 60 or62 will result in leaking of fluid from the regions 72 or 74 to theexterior environment, generally decreasing the pressure in the regions72 and 74. While loss of sealing integrity at both sealing stages of thering gasket 44 may result in increasing or decreasing pressure withinthe regions 72 and 74 depending on the magnitude of failure at eachstage of the ring gasket 44, the corresponding change in pressure canstill be monitored and correlated to a loss of sealing integrity.

This capability of monitoring pressure and sealing integrity may bebeneficial in a number of applications, including during well fracturingoperations. One example of a method for performing fracturing operationsis generally represented by block diagram 76 in FIG. 7. In thisembodiment, the method includes installing a gasket (such as ring gasket44) at a fracturing connection, as represented in block 78. For example,the installation may include positioning a ring gasket in a sealinggroove of a wellhead component and then joining a fracturing tree to thewellhead component with fasteners such that the ring gasket also engagesa sealing groove of the fracturing tree. In block 80, the ring gasket isthen set into sealing engagement by applying a preload to the gasket(e.g., by tightening fasteners 36 joining the fracturing tree 20 and thewellhead component 30).

After the ring gasket is set, fracturing of the well may begin asindicated at block 82. It is noted that fracturing trees oftenexperience significant vibration and bending moments as a result ofreceiving and transmitting high-pressure fracturing fluids into thewell. Excessive forces on the fracturing tree could cause the ringgasket to lose sealing engagement at a sealing surface and result inleaking of fracturing fluid. But in accordance with the presenttechnique, the sealing integrity of the ring gasket may be monitored(e.g., through the pressure monitoring described above) duringfracturing of the well as indicated at block 84. A sudden pressurechange detected within a region between the sealing stages of the ringgasket 44 (e.g., within the regions 72 or 74) may be indicative of lossof sealing integrity and the fracturing operation may be suspended(block 86) to reduce or prevent leaking of fluid at the ring gasket 44.In such an instance, further integrity testing may be performed aftersuspension of fracturing and suitable adjustments may be made by theoperator. For instance, additional preload may be applied or the ringgasket may be replaced, if needed. In some cases, the loss of sealingintegrity at one stage of the ring gasket 44 may be detected before lossof sealing integrity at the other stage of the ring gasket 44, which mayallow the fracturing operation to be suspended before any leaking offracturing fluid through the connection to the surrounding environmentcan occur. Of course, it will be appreciated that the fracturingoperation may also be completed (i.e., also end at block 86) withoutloss of sealing integrity at the ring gasket 44.

While the aspects of the present disclosure may be susceptible tovarious modifications and alternative forms, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. But it should be understood that the invention is notintended to be limited to the particular forms disclosed. Rather, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by thefollowing appended claims.

1. A well-fracturing system comprising: a wellhead component including asealing groove; a fracturing tree coupled to the wellhead component suchthat the sealing groove of the wellhead component is aligned with anadditional sealing groove of the fracturing tree; and a ring gasketdisposed between the wellhead component and the fracturing tree withinthe sealing groove and the additional sealing groove, wherein the ringgasket is a multi-stage sealing gasket including: a first sealing stagein the form of an outer end of the multi-stage sealing gasket havingsurfaces that seal against the sealing groove and the additional sealinggroove, respectively; a second sealing stage in the form of an inner endof the multi-stage sealing gasket having surfaces that seal against thesealing groove and the additional sealing groove, respectively; and arecess in a surface of the multi-stage sealing gasket between the firstand second sealing stages.
 2. The well-fracturing system of claim 1,wherein the wellhead component includes a test port that enables testingof pressure within the sealing groove.
 3. The well-fracturing system ofclaim 2, including a pressure port through the multi-stage sealinggasket, wherein the pressure port fluidly connects a region in thesealing groove between the multi-stage sealing gasket and the wellheadcomponent with another region in the additional sealing groove betweenthe multi-stage sealing gasket and the fracturing tree to enable testingof pressure within both regions via the test port.
 4. Thewell-fracturing system of claim 2, wherein the wellhead component andthe fracturing tree are coupled together via a flanged connection. 5.The well-fracturing system of claim 4, wherein the test port is in aflange of the wellhead component and is fluidly connected to the sealinggroove.
 6. The well-fracturing system of claim 5, wherein the flange ofthe wellhead component is an API flange.
 7. The well-fracturing systemof claim 6, wherein the flange of the wellhead component is a 6BXflange.
 8. The well-fracturing system of claim 7, wherein the ringgasket has a lower gasket setting load than a BX ring gasket.
 9. Thewell-fracturing system of claim 1, wherein the recess in the surface ofthe multi-stage sealing gasket includes a first recess between surfacesof the first and second sealing stages that seal against the sealinggroove of the wellhead component and a second recess between surfaces ofthe first and second sealing stages that seal against the additionalsealing groove of the fracturing tree.
 10. The well-fracturing system ofclaim 1, wherein the ring gasket is a stainless steel ring gasket. 11.The well-fracturing system of claim 1, wherein pressure within therecess of the multi-stage sealing gasket during fracturing is less thanbore pressure within the wellhead component and greater thanenvironmental pressure outside of the wellhead component.
 12. Awell-fracturing system comprising: a wellhead component including a 6BXflange; a fracturing tree connected to the 6BX flange; and a non-BX ringgasket disposed in sealing grooves of the 6BX flange and the fracturingtree.
 13. The well-fracturing system of claim 12, comprising a test portfluidly connected to at least one of the sealing grooves of the 6BXflange or the fracturing tree.
 14. The well-fracturing system of claim12, wherein the non-BX ring gasket includes a pair of opposing recessesbetween inner sealing surfaces of the non-BX ring gasket and outersealing surfaces of the non-BX ring gasket.
 15. The well-fracturingsystem of claim 12, wherein the wellhead component includes a tubingspool.
 16. A well-fracturing method comprising: beginning fracturing ofa well using a fracturing tree coupled to a wellhead assembly; andmonitoring, via pressure testing, sealing integrity of a gasket betweenthe fracturing tree and the wellhead assembly during the fracturing ofthe well.
 17. The well-fracturing method of claim 16, wherein monitoringthe sealing integrity of the gasket includes monitoring pressure withina recess in which the gasket is disposed.
 18. The well-fracturing methodof claim 17, wherein monitoring the pressure within the recess includesmonitoring the pressure within a region between two sealing stages ofthe gasket in the recess.
 19. The well-fracturing method of claim 16,comprising detecting, via the monitoring of the sealing integrity of thegasket, a loss of preload on the gasket during fracturing of the well.20. The well-fracturing method of claim 19, stopping fracturing of thewell in response to the detected loss of preload on the gasket.